In Vitro Prenylation of the Small GTPase Rac13 of Cotton (original) (raw)

19951 MOI Cen Cenet 248: 43-51) has identified a gene in cotton (Gossypium hirsutum), Racl3, that encodes a small, signaltransducing CTPase and shows high expression in the fiber at the time of transition from primary to secondary wall synthesis. Since Racl3 may be important in signal transduction pathway(s), regulating the onset of fiber secondary wall synthesis, we continue to characterize Rac73 by determining its ability to undergo posttranslational modification. In animals Rac proteins contain the C-terminal consensus sequence CaaL (where "a" can be any aliphatic residue), which is a site for geranylgeranylation (B.T. Kinsella, R.A. Erdman, W.A. Maltese [19941 J Biol Chem 266: 9786-9794). We have identified activities in developing cotton fibers that resemble in specificity the geranylgeranyl-and farnesyltransferases of animals and yeast. In addition, using prenyltransferases from rabbit reticulocytes, we show that Rac73, having a C-terminal sequence of CAFL, can serve as an in vitro substrate for geranylgeranylation but not farnesylation. However, the presence of the uncommon penultimate F residue appears to slow the rate of prenylation considerably compared with other acceptors. Copyright Clearance Center: 0032-0889/ 96/ 112/ 1491 /O7 LITERATURE ClTED Basra AS, Malik CP (1984) Development of the cotton fiber. Int Rev Cytol 89: 65-113 Biermann BJ, Morehead TA, Tate SE, Price JR, Randall SK, Crowell D N (1994) Nove1 isoprenylated proteins identified by an expression library screen. J Biol Chem 269: 25251-25254 Boguski MS, McCormick F (1993) Proteins regulating Ras and its relatives. Nature 366: 643-654 Clarke S (1992) Protein isoprenylation and methylation at carboxyl-terminal cysteine residues. Annu Rev Biochem 61: Delmer DP, Pear J, Andrawis A, Stalker D (1995) Genes for small